The present invention relates to activated coatings.
Activated carbon granules, produced from organic precursors such as coal, wood, nutshells, etc., or activated carbon fibers, produced from organic and synthetic precursors, have been used to remove contaminants from waste streams. The precursor is usually heated until carbonized, and then activated. Activation is achieved typically by heating the carbonized material in an oxidizing environment. Activated carbon typically contains at least 95 wt % carbon.
It is also known to chemically activate carbon, but this alternative method is usually limited to woody and coal precursors. This process involves carbonizing the parent material after impregnation, with, for example phosphoric acid, zinc chloride, or potassium hydroxide. In such an activation process, there is no direct solution or melting between parent material and chemical reagent, but primarily an impregnation process. Usually the temperature range for such activation is 600 to 900xc2x0 C. and creates a pelletized product.
Activated carbon fibers, suffer from some disadvantages. For example, extreme weight loss results during the production of activated carbon fibers, limiting their cost-effectiveness. Furthermore, activated carbon fibers are usually brittle or frangible, due to producing these fibers by carbonization at high temperatures; these poor mechanical properties limit their utility to systems containing some sort of mechanical support, and make it difficult or expensive to produce forms such as woven fabrics, felts and papers.
Glass or mineral fibers, coated with activated carbon, have been prepared. For example, U.S. Pat. No. 5,834,114 describes glass or mineral fibers coated with activated carbon prepared by coating a glass or mineral fiber substrate with a resin, cross-linking the resin, heating the coated fiber substrate and resin to carbonize the resin, and exposing the coated fiber substrate to an etchant to activate the coated fiber substrate. Also, Unexamined German Patent no. 3,339,756 A1 describes fibers coated with activated carbon. The fibers are coated with a carbonizable substance optionally containing a dehydrating substance, and carbonized at 800-1100xc2x0 C., and then formed into activated carbon by heating at a temperature of at least 750xc2x0 C. in the presence of oxygen, ammonia, water vapor or carbon dioxide, or a mixture of these gases. If the carbonizable coating melts before carbonization, it may be heated in air or another oxidizing agent to approximately 200-300xc2x0 C. to form an infusible layer, avoiding loss due to drippage during carbonization.
In a first aspect, the present invention includes a composite containing substrate fibers, and an activated organic coating, on the substrate fibers. The substrate fibers have a softening or decomposition temperature of at most 500xc2x0 C.
In a second aspect, the present invention includes a method of making a composite, including heating a coating mixture, to form an activated organic coating. The coating mixture is on substrate fibers, and the coating mixture contains a polymeric material and an activating agent.
In a third aspect, the present invention includes a method of making a composite, including mixing together a set of ingredients to form a first mixture; coating substrate fibers with the first mixture; and heating the coating mixture, to form an activated organic coating. The set of ingredients contains a volatile solvent, a polymeric material, and an activating agent. The polymeric material is soluble in the volatile solvent, and the heating is at a temperature of 150-400xc2x0 C.
In a fourth aspect, the present invention includes a composite, containing substrate fibers, and a coating, on the substrate fibers. The coating has a B.E.T. surface area of 50 to 1800 m2/g, and a nitrogen content of 12 to 20 wt. %.
In a fifth aspect, the present invention includes a composite, containing substrate fibers, and a coating, on the substrate fibers. The coating has a B.E.T. surface area of at least 50 m2/g, and a carbon content of at most 85 wt %.
The term xe2x80x9csolublexe2x80x9d means that at least 0.1 mg of the solid will dissolve in 1 liter of the solvent at room temperature.
The term xe2x80x9cvolatile solventxe2x80x9d means that the solvent has a vapor pressure of at least 10 mTorr at 200xc2x0 C.
The term xe2x80x9cactivated organic coatingxe2x80x9d means a material that contains carbon and has a B.E.T. surface area of at least 50 m2/g.
The term xe2x80x9cpolymeric materialxe2x80x9d means a composition that contains at least one organic polymer.
The term xe2x80x9cactivating agentxe2x80x9d means an acid or base, including Lewis acids and bases, that will convert a polymeric material into an activated organic coating upon heating to a temperature of 400xc2x0 C. or less.